Effect of Lignin on the In Vitro Digestibility of Wood Pulp

Abstract

IN vitro dry matter digestion and chemical analyses are shown for wood pulps with varying lignin contents made by the kraft, or sulfate, process from paper birch, red oak, red pine and Douglas-fir wood. At high lignin contents, the pulps from the hardwood species are more digestible than pulps from softwood species. At lignin contents below 7%, the pulps have about equal digestibility. A curve of digestibility vs. extent of delignification shows that digestibility depends upon how much of the original lignin has been removed. Also it indicates that, in general, softwoods increase more slowly in digestibility as lignin is removed than do hardwoods. Calculations from published in vivo data on 40 wood pulps made by 10 different pulping methods are given to show that digestibility of a pulp depends upon the quantity of lignin removed but not upon the method of removal. Copyright © 1973. American Society of Animal Science . Copyright 1973 by American Society of Animal Science